1. Field of the Invention
The present invention relates to a part-mounting structure for a sandwich structure constituted by a core layer and skin layers, and more particularly to a part-mounting structure for a vehicle body constituted by such a sandwich structure.
2. Description of Related Art
Recently, to reduce vehicles' weights and to increase productivity by reducing vehicles' parts, it was proposed to use composite structures such as fiber-reinforced plastics for vehicle bodies, and they are now partly put into practical use.
Such composite structures are in general sandwich structures constituted by cores coated with skin layers on both surfaces. Various proposals were made to use foamed plastics for cores (Japanese Patent Publication Nos. 46-36329 and 55-43912Japanese Utility Model Laid-Open No. 63-30276, U.S. Pat. Nos. 4,559,274 and 4,573,707, etc.), and to use honeycomb structures for cores (Japanese Patent Laid-Open No. 47,32521, Japanese Utility Model LaidOpen Nos. 57-114774, 62-174935 and 62-174978, etc.). It was also proposed to use for vehicle bodies sandwich structures whose core portions are partly hollow (Japanese Utility Model Laid-Open No. 62-166136, etc.).
However, in such sandwich structures, if parts such as engines, suspension beams, upper arms, radius rods, dampers, seat slide rails, etc. are mounted to them directly by screws, etc., the screws would not be able to be firmly fixed, and the mounting strength of parts would be insufficient. Particularly, since various parts such as engines mounted to the vehicle body are heavy and subjected to vibrations, mere threading, welding or bonding for mounting the parts onto the skin layers of the sandwich structures would result in an insufficient mounting strength. In addition, once peeling takes place in the adhesion layer, the breakage thereof would propagate quickly.
Also, since a floor panel, a lower part of the vehicle body, is provided with various parts such as seats, a side brake, a change lever, etc., and is subjected to a large stress, it should have part-mounting structures having extremely high strength.
Further, if part-mounting brackets are used to mount parts to the vehicle body, the reduction of the number of parts and vehicles' weights would not be achieved. In addition, since the brackets are generally bulky, the mounting space would be inevitably large.
In addition, since the seat slide rails are portions to which the overall weight of a passenger is applied, and are likely to be subjected to a large load upon sliding the seat, slide rail-mounting structure is required to have high strength.